Registration Dossier
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EC number: 931-288-4 | CAS number: -
Endpoint summary
Administrative data
Description of key information
Additional information
Summary
Stability (hydrolysis):
In a screening test at 50°C the HDI Uretdion was found to hydrolyse within less than 2 hours at pH values of 4, 7, and 9. Approximate mean half-lives far below 1 day at 25°C were estimated at any pH and environmental relevant temperatures. No degradation products could be detected. Typical hydrolysis products of isocyanates are mainly monomeric or polymeric urea components (Bayer Industry Services, 2006) and substances with free amino functions.
Based on the determination of the isocyanate function, the half-time of HDI Uretdione in the acetonitrile/water solution is approx. 6.1 hours at room temperature (23 °C). Hydrolysis products have not been elucidated (Bayer AG, 2000).
However similar substances containing several isocyanate groups like HDI, MDI are known to react rapidly with water forming insoluble oligomeric and polymeric ureas. The mentioned corresponding diamine is only a theoretical worst-case assumption in order to have a basis for assessment but which in reality reflects only insignificant traces.
Phototransformation in air:
The atmospheric oxidation rate constant of the main component HDI Uretdion is 25.0 * 10-12cm3/(molecule *s) and its atmospheric half-life is 15.4 hrs (Currenta, 2014c).
The atmospheric oxidation rate constant of the corresponding diamine of the main component HDI Uretdion is 86.1 * 10-12cm3/(molecule *s) and its atmospheric half-life is 4.5 hrs (Currenta, 2014d).
Biodegradation (in water, screening test):
HDI Uretdion is “not readily biodegradable”. Within 28 days only 1 % of the test substance was degraded (Closed Bottle Test), (Bayer AG, 2000).
In a 'Modified MITI (II) Test' with adapted inoculum only 18 % degradation of HDI Uretdion could be obtained within 28 days (Currenta, 2009). Therefore the test item is considered to be "Not Inherently Biodegradable".
This result is used for assessing the behaviour of the substance in STPs.
Bioaccumulation:
The direct and indirect exposure of the aquatic compartment is unlikely because HDI Uretdion hydrolysis completely in water within far below 24 hours at environmental relevant concentrations. Therefore the BCF-values were calculated. Bioconcentration factors (BCF) of 457 and 143 L/kg wet-wt for the main component HDI Uretdion and its corresponding diamine were obtained (Currenta, 2014e/2014f).
Even the corresponding diamine of HDI Uretdion (which is onyl hypothetical)
with a bioconcentration factor of 143 L/kg wet-wt does not have high bioaccumulation potential (Currenta, 2014f).
Adsorption / desorption:
The QSAR determination of the carbon partition coefficient for 1,3-Diazetidine-2,4-dione, 1,3-bis(6-isocyanatohexyl) (CAS 23501-81-7) using the model KOCWIN included in the Estimation Program Interface (EPI) Suite v4.11 revealed values of 33330 L/kg (logKow method) and 18870 L/kg (MCI method) for the unaffected molecule of the substance as any decomposition (e.g. hydrolysis) of the substance is not taken into account by the program (Currenta, 2014g). The organic carbon partition coefficient (Koc) of the corresponding diamine, 1,3-Diazetidine-2,4-dione, 1,3-bis(6-aminohexyl) was predicted using the QSAR calculation of the Estimation Program Interface (EPI) Suite v 4.11. The Koc was estimated to be 799.5 L/kg (logKow method), and 642.2 L/kg (MCI method). The results relate to the unaffected molecule of the substance as any decomposition (e.g. hydrolysis) of the substance is not taken into account by the program (Currenta, 2014h).
Volatilisation
With a vapour pressure of about 0.00029 Pa at 20 °C volatilisation of the substance is unlikely.
Distribution modelling
HDI Uretdion hydrolyses rapidly in the presence of water yielding a complex mixture of oligomeric and polymeric urea derivatives which are non-soluble in water. Due to the rapid hydrolysis of HDI Uretdion, a transport of the substance between environmental compartments is unlikely.Consequently, a calculation of the distribution between the environmental compartments according to the Mackay fugacity model level 1 or 3 is not suitable.
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